MILK and MILK PRODUCTS

MILK and MILK PRODUCTS

MILK and MILK PRODUCTS Technolog)', chemistry and microbiology Alan H. Varnam Consultant Microbiologist Southern Biological Reading UK and Jane P. Sutherland Head of Food and Beverage Microbiology Section AFRC Institute of Food Research Reading UK I~nl SPRINGER-8CIENCE+BUSINESS MEDIA, B.v.

First edition 1994 1994 Alan H. Varnam andjane P. Sutherland Originally published by Chapman and Hall in 1994 Softcover reprint of the hardcover 1st edition 1994 Typeset in Garamond ITC by Faleon Graphie Art Ltd, Wallington, Surrey ISBN 978-1-4613-5732-2 ISBN 978-1-4615-1813-6 (ebook) DOI 10.1007/978-1-4615-1813-6 Apart from any fair dealing for the purposes of research or private study, or eritieism or review, as permitted under VK Copyright Designs and Patents Aet, 1988, this publieation may not be reprodueed, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the ease of reprographie reproduetion only in aeeordanee with the terms of the licenses issued by the Copyright Lieensing Agency in the VI(, or in aeeordanee with the terms of licences issued by the appropriate Reproduetion Rights Organization outside the UK.. Enquiries eoneerning reproduetion outside the terms stated here should be sent to the publishers at the London address printed on this page. The publisher makes no representation, express or implied, with regard to the aeeuracy of the information eontained in this book and eannot accept any legal responsibility or liability for any errors or omissions that may be made. A eatalogue reeord for this book is available from the British Library Library of Congress Cataloging-in-Publieation data available @ Printed on permanent aeid-free text paper, manufaetured in aeeordanee with the proposed ANSIINISO Z 39.48-199X and ANSI Z 39.48-1984

Contents Preface A note on using the book Acknowledgements vii ix x 1 Introduction 1 1.1 The nature of milk 1 1.2 Milk production as an activity of man 1 1.3 Biosynthesis of milk 6 1.4 The composition of milk 8 1.5 The flavour and sensory properties of milk 27 1.6 Potential hazardous substances in milk 28 1.7 The microbiology of milk at farm level 33 2 Liquid milk and liquid milk products 42 2.1 Introduction 42 2.2 Technology 46 2.3 Chemistry 76 2.4 Microbiology 88 3 Concentrated and dried milk products 103 3.1 Introduction 103 3.2 Technology 104 3.3 Chemistry 138 3.4 Microbiology 149 4 Dairy protein products 159 4.1 Introduction 159 4.2 Technology 162 4.3 Chemistry 179 4.4 Microbiology 180

vi Contents 5 Cream and cream-based products 183 5.1 Introduction 183 5.2 Technology 183 5.3 Chemistry 211 5.4 Microbiology 216 6 Butter, margarine and spreads 224 6.1 Introduction 224 6.2 Technology 227 6.3 Chemistry 257 6.4 Microbiology 268 7 Cheese 275 7.1 Introduction 275 7.2 Technology 276 7.3 Chemistry 321 7.4 Microbiology 332 8 Fermented milks 346 8.1 Introduction 346 8.2 Technology 347 8.3 Chemistry 370 8.4 Microbiology 380 9 Ice cream and related products 387 9.1 Introduction 387 9.2 Technology 391 9.3 Chemistry 420 9.4 Microbiology 426 Bibliography 432 Index 436

Preface Milk has been an important food for man since the domestication of cattle and the adoption of a pastoralist agriculture. It is also the most versatile of the animal-derived food commodities and is a component of the diet in many physical forms. In addition to milk itself, a rural technology evolved which permitted the manufacture of cheese, fermented milks, cream and butter. At a later date, successive advances in technology were exploited in the manufacture of ice cream, concentrated and dried milks and, at a later date, of ultra-heat-treated dairy products, new dairy desserts and new functional products. At the same time, however, dairy products have been increasingly perceived as unhealthy foods and a number of high quality dairy substitutes, or analogues, have been developed which have made significant inroads into the total dairy food market. Paradoxically, perhaps, the technology which, on the one hand, presents a threat to the dairy industry through making possible high quality substitutes offers, on the other hand, an opportunity to exploit new uses for milk and its components and to develop entirely new dairy products. Further, the development of products such as low fat dairy spreads has tended to blur the distinction between the dairy industry and its imitators and further broadened the range of knowledge required of dairy scientists and technologists. One of the most striking features of the traditional dairy industry is the manner in which technology, chemistry and, subsequently, microbiology were integrated to allow the manufacture of high quality and safe products. It is considered that a similar integration of disciplines is required both to enable the dairy industry to meet the many future challenges, and also to permit the student of Food Science, Food Technology and related subject areas to gain a true knowledge of the nature of dairy products. In writing this book, we have been very conscious of the requirements,

viii Preface not only of undergraduate and equivalent students, but of the new graduate entering industry and facing new and potentially frightening situations. To this end, the book is structured to meet the requirements both of the student, with a basic knowledge of chemistry, biochemistry and microbiology and of persons working in the dairy industry. The basic approach is to discuss the manufacturing process in the context of technology and its related chemistry and microbiology, followed by a more fundamental appraisal of the underlying science. The dairy industry is defined in a broad context and information is induded on imitation products and analogues. A number of innovations have been adopted in the presentation of the book. Information boxes and points are used to place the text in a wider scientific and commercial context, and exercises are induded in most chapters to encourage the reader to apply the knowledge gained from the book to unfamiliar situations. It is also our firm belief that the control of food manufacturing processes should be considered as an integral part of the technology and for this reason control points, based on the HACCP system, are induded where appropriate.

A note on using the book EXERCISES Exercises are not intended to be treated like an examination question. Indeed in many cases there is no single correct, or incorrect, answer. The main intention is to encourage the reader in making the transition from an acquirer of knowledge to a user. In many cases the exercises are based on 'real' situations and many alternative solutions are possible. In some cases provision of a full solution will require reference to more specialist texts and 'starting points' are recommended. CONTROL POINTS In most chapters control points, derived from HACCP analysis, are included for the main processing stages. These are linked to process flow-diagrams. Points designated as CCP 1 are those which ensure elimination of a hazard; those designated CCP 2 are either points at which a hazard can be controlled but not eliminated or points which must be controlled to ensure satisfactory product quality. The inclusion of control points is intended to encourage a way of thinking in which control is an integral part of technology. If required, readers may use the control points included to further develop the HACCP approach for themselves.

Acknowledgements The Authors wish to thank all who gave assistance in the writing of this book. Special appreciation is due to: Debbie. and Phil Andrews for providing, respectively, hand drawn and computer-generated illustrations. Dr G. Ellen, NIZO, The Netherlands and Dr A.I. Alvarez de Felipe, University of Leon, Spain for providing electron micrographs. Those manufacturers of food processing equipment, food ingredients and laboratory equipment, who willingly provided information concerning the 'state-of-the art' (APV Pasilac Anhydro AlS, Copenhagen, Denmark; Cerestar SAINV, Brussels, Belgium; Charm Sciences Inc., Malden, Massachusetts USA; Gadan UK Ltd, Wem, UK; Niro Atomizer AlS, Soeborg, Denmark; Oxford Instruments Ltd, Abingdon, UK; R.P. Texel Ltd, Stockport, UK; G.E.A. Wiegand GmbH, Ettlingen, Germany). The libraries of the AFRC Institute of Food Research, Reading Laboratory and the University of Reading for their assistance in obtaining information. Our colleagues in Reading and elsewhere for their help and interest during the preparation of the book.